The leading cause of lower back pain arises from rupture or degeneration of lumbar intervertebral discs. Pain in the lower extremities is caused by the compression of spinal nerve roots by a bulging disc, while lower back pain is caused by collapse of the disc and by the adverse effects of articulation weight through a damaged, unstable vertebral joint. One proposed method of managing these problems is to remove the problematic disc and replace it with a prosthetic disc that allows for the natural motion between the adjacent vertebrae (“a motion disc”).
Surgery for the revision of an anterior lumbar motion disc, while rare, is particularly challenging due to adhesion that form following the mobilization of the great vessels during the initial procedure. The tenacity of these adhesions coupled with the fragility of the vena cava enhances the potential that this venous structure may become torn or ruptured during the revision surgery. Considering these factors and the technically demanding repair required, there is significant risk to the patient.
Anti-adhesion sheets have been proposed for use in both anterior motion disc implantation and anterior intervertebral fusion surgeries in order to maintain a dissection plain to the surgical site to reduce the tenacity, area and density of the adhesions. Historically, there have been many proposals for anti-adhesion devices for use in hernia repair and for the prevention of intra-abdominal adhesions. One such example of an anti-adhesion device for hernia repair is found in US Published Patent Application No. 2005/0192600. Such devices do not have to take into account the prevention of damage to great vessel walls. Anti-adhesion devices have also been used in the posterior region of the spine to prevent dural adhesions. These devices are typically described as being in the form of a gel, a thick plate or a mesh.
U.S. Pat. No. 6,869,938 (“Schwartz”) discloses an anti-adhesion material that is available as either a membrane or gel, specifically comprising a polyacid, a polyalkylene oxide, and a water soluble multivalent cation.
U.S. Pat. No. 6,475,219 (“Shelokov”) discloses an anti-adhesion barrier for use in spinal surgery, wherein the barrier has a pleat to allow stretching as a consequence of movement between vertebral bodies to which the barrier is connected. Shelokov further discloses that the anti-adhesion barrier may have a radiopaque tab to aid in locating the device once it is in a working position. Shelokov further discloses that the anti-adhesion barrier has a concave face having a radius of curvature equal to the radius of curvature of the vertebral body to which it is attached. See FIG. 1 of Shelekov. Shelokov further discloses that the anti-adhesion barrier has holes for receiving bone fasteners so that the device may be secured to the vertebral bodies.